The .sup.131 J-radioactive iodine has been used for some time routinely and with good success for the therapy of many thyroid complaints. The patient is given .sup.131 J-iodine, sometimes .sup.125 J-iodine, in the form of a carrier free iodide in activities of a few mCi up to 300 mCi at one time as a radioactive therapy. Dependent on the storing of the thyroid tissue, of the primary thyroid tumor or of the distant metastases in case of the thyroid carcinoma, and depending on the iodinations, iodization and incretion of the thyroid gland, a more or less large part of radioactive iodine given is excreted as inorganic iodide or organically bound iodine (L-triiodine thyronine, L-thyroxine, mono iodine and di iodine thirosine or on plasmatic proteines) by the renal manner. The .sup.131 J-iodine activities, which are secreted via the salivary glands and stomach secretion, are partly re-absorbed in the ileum and partly secreted with the stool. The radioactive iodine secretions by the stool is very small as compared to the renal eliminations. The radioactive iodine excretion by way of the kidneys is within the range of 50.varies.70%, in case of the thyroid metasteases even up to 83% of the administered activity in 48 hours. On the other hand, the excretion of radioactive iodine in the stool amounts to a maximum of 6% of the applied activity. According to measurements, the total excretion of radioactive iodine via the kidneys, depending on the thyroid gland situation, lies within the range between 70-90% of the applied activity.
The radioactive iodine urine excretion depends indirectly on the iodination and directly on the iodization or incretion of the thyroid gland. It also depends on these processes whether the iodine is excreted in an inorganic form or organically bound via the urine. In case of an increased iodine storage as happens in case of therapy of thyroid carcinoma-distant metastases after thyroid elimination, the percentage of the radioactive iodine excretion is very high and reaches almost 90% of the applied activity in 48 hours. The excreted iodine is present in the form of inorganic iodine. On the contrary, in case of hyperthyrotoxicoses and toxic adenoma, the radioactive iodine adsorption is accelerated and thus the excretion of the administered radioactive iodine is essentially decreased. In the first 48 hours only 17 to a maximum of 30% of the inorganic iodine is eliminated. The further excretion of radioactive iodine takes place on a delayed basis. On the basis of the higher and accelerated metabolism, the radioactive iodine is present partly also organically bound in triiodine thyronine, thyroxine, mono and di iodine thyronine or in plasmatic proteins.
It was found by means of whole body measurements of patients with thyroid malignancies under radioactive iodine therapy, that 87-90% of the applied activity is excreted in 48 hours at the latest in 72 hours. The total excretion amounts then in 5 days to 98-99.5%.
Very high activities of averagely 100-200 mCi must be administered at one time in case of patients with thyroid malignancies as a therapy. That means that in the first 2-3 days 80-180 mCi of .sup.131 J-iodine are eliminated from the patient's body through the kidneys. Such urine activities are considerably above the values which according to the radiation protection regulations are permitted to be delivered into the public canalization. There are only very few nuclear medical clinics with special lavatories with their own insulated monitored flushing systems and fade-away tank, suitable for the collection of radio-nuclides. The only other legal possibility lies in collecting the individual portions of highly radioactive excretions and their storage in a fade-away space at least for 10 half value times (=80 days). At the same time, there always is a serious danger for the nursing personnel because of charges of radiation. Moreover, in the case of this process contamination of individuals, rooms and apparatuses are very difficult to avoid, besides a very cumbersome task with human excretions. The storage of the highly active secretions moreover produces conservation problems for the prevention of fermentation processes. In many places, the collection and storage of radioactive excretions is completely passed over and the patient is permitted to use standard lavatories. As a result, every day hundreds of millicurie of .sup.131 J-iodine activities are discharged daily into the sewage on the basis of medical use.
In order to avoid the unpleasant manipulation and storage of highly active urine, a process has become known which is based on the binding of the radioactive iodine to an ion exchanger. This process, which at first glance seems simple and plausible, has however a few unacceptable disadvantages in case of its practical execution:
(1) The ion exchanger loses its ability of exchanging the .sup.131 J-iodine fairly soon; the ion exchanger cartridges must therefore be replaced often.
(2) The ion exchanger column is plugged up by the inorganic and organic substances and micro-particles present in the urine even in case of use of a coarse-grained ion exchanger, so that the urine will soon only flow by drops through the column.
(3) The regeneration of an ion exchanger is not meaningful because of the enrichment of the separation column with highly radioactive .sup.131 J-iodine. Thus, this process is fairly expensive because of the relatively high price of the ion exchanger and also quite costly because of the frequent replacement of the cartridge (3 to 4 times per patient in case of an average volume of urine of 200 ml).
(4) Iodine is caught selectively only in the organic form, for example, as iodide or iodade. The organically bound iodine can not be separated with this process. That means that even beginning with four days, more than 15% of the radioactive iodine will flow through the ion exchanger column.
All hitherto used processes for the removal of the radioactive iodine from the urine are cumbersome, constitute a potential danger for additional charge by radiations of the nursing personnel or have a lower and uncertain yield.
It is the task of the present invention to create a process for the removal of radioactive iodine from a liquid, especially from urine, which can be executed in a simple and continuous manner without contaminations of persons, rooms and apparatuses, which furthermore has a reliable and high yield and which produces a solid, compact and correspondingly small volume of radioactive substance which may be stored radiation-safe easily and without danger up to the fading away of the radioactivity.
Another task of the present invention consists in creating an arrangement, by means of which the above mentioned process may be carried out automatically without manual intervention.
According to the invention, the process for the removal of radioactive iodine from a liquid, especially from urine, is characterized in that a predetermined quantity of the liquid free of solids, and containing the radioactive iodine is collected in continuously successive processing steps, in that always a dosed quantity of at least a first reaction solution containing a carrier substance for the radioactive iodine and of a second reaction solution, containing a salt of a heavy metal is fed to this quantity of liquid, in that the fed-in reaction solutions are mixed with the liquid during a predetermined time for the formation of an insoluble, radioactive precipitate, in that the liquid containing the radioactive precipitate as a suspension is filtered in order to separate the radioactive precipitate from the liquid, and in that the liquid, freed at least approximately of radioactive components, is collected for the purpose of discharge into a canalization system, whereby these processing steps are carried out in an automatic course.
The arrangement for carrying out the process has been characterized according to the invention by a reaction chamber equipped with a suction line for the liquid containing radioactive iodine, which chamber has a level sensor, a mixing apparatus and a pressure pump for conveying of the liquid located in the reaction chamber, into the outlet line, and to which at least two tanks for the reaction solutions, equipped always with a dosing arrangement, have been assigned, by a filtration unit, connected releasably to the output line of the reaction chamber, the liquid-output line of which leads to collecting tank having an outlet, the outlet of which may be connected with the canalization system via a discharge valve, and by a programmable, electric control unit, the control inlets or outlets of which are connected with the level sensor, the mixing arrangement, the pressure pump and the dosing arrangements of the reaction chamber as well as with the discharge valve of the collecting tank.